Plasma cell tumors have been shown to carry tumor associated transplantation antigens that can induce immune responses in syngeneic animals resulting in tumor rejection. The key objectives of this proposal are to identify the various antigens that are present on plasmacytomas, to characterise these antigens in terms of surface localisation and chemical structure, and to individually determine their ability to induce immune responses effective against the living tumor. This will include examination of A type particles and C type RNA viruses present in these tumors for both viral envelope antigens and for cell surface antigens; differentiation and alloantigens of plasma cells, and oncofetal antigens. The studies will involve (1) Characterising NZB and BALB/c inbred and hybrid derived plasmacytomas for the presence and surface location of a range of MuLV associated antigens and virions, and then studying lines deficient in only some of these for susceptibility to immune responses to plasmacytomas. (2) isolating viral particles from plasmacytomas and testing these for their ability to induce immunity to transplanted tumors or to the induction of plasmacytomas. (3) solubilising and chemically characterising viral antigens and cell surface antigens of plasmacytomas and ascertaining their potential to induced immunity, or to block previously induced responses. (4) comparing the ability of other cell surface antigens such as immunoglobulins (idiotype antigens) or antigens shared with fetal hematopoietic stem cells, to induce or block immunity to plasmacytomas.